IX
ON THE PRESSURE OF SATURATED
MERCURY-VAPOUR
(Wiedemann's Annalen, 17, pp. 193-200, 1882.)
1
THE following determinations of the pressure of saturated
mercury-vapour suggested themselves as a continuation of
previous experiments on evaporation. In working out the
latter I at first used the data given by Regnault; but these
did not prove suitable, as the following will show. I plotted
out the results of the experiments made by the second method,2
taking as abscissæ the amounts which evaporated in unit time
from a surface at a given temperature, and as ordinates the
corresponding pressures, and thus obtained series of points
lying approximately on straight lines. By prolonging these
straight lines a very little beyond the observed interval, I
found the pressures which corresponded to zero evaporation,
and which must therefore have represented the saturation-
pressures. The numbers thus found were always smaller than
Regnault's. That this might be explained by errors in the
latter was first suggested to me by Hagen's experiments;
but his data, again, did not agree well with my results.
Hagen himself suspected that his values were too small at
temperatures above 100°; and as these were just the tempera-
tures which interested me, I decided to investigate the matter
myself.
3
The experiments were first carried on as a continuation
of the experiments on evaporation. The measurements were
1 See VIII. p. 186. 2 See p. 191. 3 See Wied. Ann. 16, p. 610, 1882.